The present invention relates to a mould for composite casting of a one piece-cast tool, which comprises at least a first portion which includes the working component of the tool and which is manufactured from steel, and a second portion, which includes the body portion of the tool and which is manufactured from grey iron, the tool having at least a first mould cavity section for the steel and a second mould cavity section for the cast iron and there being at least one interconnection zone between the steel and the cast iron.
The present invention also relates to a method of composite casting of a one piece-cast tool, which comprises at least a first portion which includes the working component of the tool and which is manufactured from steel, a second portion which includes the body component of the tool and which is manufactured from grey iron, the first portion being cast in at least one first mould cavity section and the second portion being cast in a second mould cavity section of the mould.
In the production of tools for sheet metal working, for example pressing, cutting and similar working operations, it has been previous practice to separately produce a tool body which has then been provided with one or more working components, i.e. that component of components which carry out the actual working operation. The production of the tool body can be put into effect by casting of grey iron or by welding taking as starting material suitably dimensioned sheet metal material with adapted material composition.
In the alternative involving a cast tool body, heat treatment is often required of the tool body after the casting, this is followed by machining in order for requisite seats, holes for guide shafts and bolts for securing the working component or working components, but also to make possible securing of the tool in a machine.
In the production of the working component or components which are intended for carrying out the working operations for which the tool is designed and constructed, the point of departure has often been bar material, in which event the working components have machined to the correct configuration, provided with apertures for fixing bolts, guide shafts and the like. This has been followed by heat treatment and additional machining, for example grinding.
To produce tool in the above-outlined manner is extremely time-consuming and expensive and is therefore often determinative of the time consumption which is required for producing new products.
It is also previously known in the art to composite cast a tool in one continuous piece, where the tool has at least one working component manufactured from steel and a body component manufactured from grey iron. Such a tool and a method for its manufacture are described in WO 03/041895.
According to this publication, both the steel and the grey iron are cast in one and the same mould, an interconnection zone being formed in the interface region between these two materials.
Using the technology as disclosed in WO 03/041895, serious difficulties have been encountered in correctly localising the interconnection zone which is created between the steel and the grey iron. This may have as a consequence that the interconnection zone is positioned in such portions of the tool where, for example, major surface area differences occur, which occasions considerable problems in mechanical strength: Problems also occur if the interconnection zone arrives in such positions where major temperature differences occur, since such differences greatly affect the quality of the interconnection zone.
It is desirable to design the mould and the method intimated by way of introduction such that the drawbacks in the prior art technology are obviated. Thus, it is desirable to make it possible, in an accurate manner, to localise the interconnection zone which is formed between the steel and the grey iron so that, with great reliability, this is at the correct position and will have a controllable temperature over as great a part of its surface as possible. In addition, it is desirable to minimise the amount of steel employed.
According to an aspect of the present invention, a mould has a dividing plane between the first and the second mould sections is substantially planar and, in the position of use of the mould, substantially horizontal and located at the intended position for the interconnection zone, that, from the first mould cavity section there leads at least one runner or duct to at least one accommodation space for possible surplus of steel and that a lower defining surface to this duct, at the discharge of the duct to the first mould cavity section in the vertical direction is located on substantially the same level as the dividing plane.
According to an aspect of the present invention, a method is characterised in that a dividing plane between the first mould cavity section and the second mould cavity section is formed to be substantially planar and positioned substantially horizontally, but at least one accommodation space is provided in the mould and that possible surplus of steel is permitted to flow from the first mould cavity section at the level of the dividing plane into the accommodation space.